1. Technical Field
The present invention relates to a liquid ejecting apparatus and a method for controlling thereof, and in particular, is useful to apply when vibrating a liquid inside a pressure generation chamber in the vicinity of a nozzle opening using a micro-vibration driving signal so as to agitate the liquid.
2. Related Art
As a liquid ejecting apparatus, for example, there is an ink jet type recording apparatus having an ink jet type recording head including a plurality of pressure generation chambers which generate pressure to eject ink droplets using a pressure generation unit formed of a piezoelectric element, an ink supply path which supplies ink from a common manifold to each of the pressure generation chambers separately and a nozzle opening which is formed in each of the pressure generation chambers and ejects the ink droplets (for example, see JP-A-2002-355961).
In the ink jet type recording apparatus described above, the ink droplets are ejected from the nozzle opening to the outside and lands on a predetermined position of a medium such as paper by applying ejecting energy to the ink inside the pressure generation chamber communicating with the nozzle opening corresponding to a printing signal.
Accordingly, in the ink jet type recording apparatus of this type, the nozzle opening faces the atmosphere. Therefore, the ink is thickened by evaporation of moisture via the nozzle opening. As a result, the ejection characteristics of the ink droplets may be adversely affected due to the thickened ink. In other words, even when just a portion of the thickened ink exists, drawbacks occur in which an ejection amount and an ejection speed of the ink droplets via the nozzle opening are changed, and variation in the landing occurs.
Therefore, in the general ink jet type recording apparatus according to the related art, it has been devised to suppress the thickening of the ink droplets by 1) always keeping the ink in the vicinity of the nozzle opening in a fresh state by moving the ink jet type recording head to other portion rather than just the media and by discharging the ink out appropriately before the ink is thickened, or 2) when the ink droplets are not ejected, micro-vibrations are generated in the pressure generation chamber by a PZT or the like that is a pressure generation unit and the ink inside the pressure generation chamber is agitated.
However, there are problems in that 1) the ink is ineffectively discarded in the method in which the ink jet type recording head is moved to a portion other than the media and the ink is discharged out appropriately before the ink is thickened, and 2) it is unclear whether or not the micro-vibration is appropriate enough to prevent the thickening of the ink even though the ink is vibrated, because the inclination of an expansion element (an element in which the ink is drawn by increasing the volume inside the pressure generation chamber; the same as below) and the inclination of a contraction element (an element in which the ink is ejected by the volume being decreased inside the pressure generation chamber; the same as below) in the micro-vibration driving signal are usually the same as each other, in the method in which the micro-vibration is generated in the pressure generation chamber and the ink inside the pressure generation chamber is agitated so that the thickening of the ink is suppressed.
In addition, the same problems are present in a liquid ejecting head, ejecting other liquids, as well as the ink jet type recording head ejecting ink.